DIFFERENTIAL GENE REGULATION IN NORMAL & TRANSFORMED KERATINOCYTES BY 1,25(OH)2

这个子项目是利用资源的许多研究子项目之一。 由NIH/NCRR资助的中心拨款提供。对子项目的主要支持 子项目的首席调查员可能是由其他来源提供的， 包括美国国立卫生研究院的其他来源。为子项目列出的总成本可能 表示该子项目使用的中心基础设施的估计数量， 不是由NCRR赠款提供给次级项目或次级项目工作人员的直接资金。 维生素D和维生素A的活性代谢产物在预防和治疗包括鳞状细胞癌(SCC)在内的多种恶性肿瘤方面显示出良好的前景。1，25(OH)2D通过其核激素受体VDR调节基因表达。VDR与维甲酸X(RXR)和维甲酸(RAR)受体结合，分别结合维生素A、9顺式维甲酸(9cisRA)和全反式维甲酸(Tra)的活性代谢产物。VDR、RXR和RAR形成异二聚体，它们通过被称为激素反应元件的基因启动子中的特定DNA序列来刺激基因表达。在正常人角质形成细胞(NHK)中，不同的维生素D应答基因具有不同的应答元件，并且受1，25(OH)2D和RA的不同调控。鳞癌细胞株(SCC)对1，25(OH)2D或RA的反应不像NHK那样。我们研究的鳞癌细胞株具有正常的VDR水平，VDR与其配体的结合正常，VDR与维生素D反应元件(VDRE)的结合正常。因此，SCC对1，25(OH)2D失去反应的原因尚不清楚。然而，最近发现VDR、RAR和RXR等核激素受体与许多共激活因子和共抑制因子相互作用，这些共激活因子和共抑制因子将与各自反应元件结合的核激素受体连接到转录起始复合体，在那里RNA聚合酶II开始转录。在之前的资助期间，我们发现在未分化的正常角质形成细胞的核提取液中，VDR的主要结合复合体是DRIP(维生素D受体相互作用蛋白)，这一复合体与甲状腺受体激活蛋白(TRAP)和激活剂招募辅因子(ARC)基本相同，后者是通过与其他核激素受体的结合来鉴定的。在角质形成细胞正常分化过程中，水滴蛋白表达下调。它与VDR的结合被两个SRC(类固醇受体共激活剂)所取代。最近，我们发现无毛起到了抑制VDR作用的作用。我们目前正在确定介导无毛对VDR的抑制作用的因素。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The active metabolites of vitamin D and vitamin A show promise in the prevention and treatment of a number of malignancies including squamous cell carcinoma (SCC). 1,25(OH)2D regulates gene expression through its nuclear hormone receptor VDR. VDR partners with the retinoic X (RXR) and retinoic acid (RAR) receptors which bind the active metabolites of vitamin A, 9cis retinoic acid (9cisRA) and all trans retinoic acid (tRA), respectively. VDR, RXR, and RAR form heterodimers, which stimulate gene expression through specific sequences of DNA in the promoter of genes called hormone response elements. Different vitamin D responsive genes have different response elements and are differentially regulated by 1,25(OH)2D and RA in normal human keratinocytes (NHK). Squamous carcinoma cell lines (SCC) fail to respond to 1,25(OH)2D or RA in the same manner as NHK. The SCC lines we have studied have normal levels of VDR with normal binding of the VDR to its ligand and normal binding of the VDR to the vitamin D response elements (VDRE). Therefore, the explanation for the loss of response of SCC to 1,25(OH)2D has been unclear. However, it has recently been discovered that nuclear hormone receptors such as VDR, RAR, and RXR interact with a number of coactivators and cosuppressors which link the nuclear hormone receptors bound to their respective response elements to the transcription initiation complex where transcription by RNA polymerase II begins. During the previous funding period we discovered that the principal binding complex to VDR in nuclear extracts from undifferentiated normal keratinocytes is DRIP (vitamin D receptor interacting protein), a complex essentially identical to TRAP (thyroid receptor activating protein) and ARC (activator-recruited cofactor) which were identified by their binding to other nuclear hormone receptors. During normal keratinocyte differentiation DRIP is downregulated. Its binding to VDR is replaced by two SRC (steroid receptor coactivator). More recently we found that hairless acts as a suppressor of VDR action. We are currently involved in determining the factors that mediate this suppressor action of hairless on VDR.